The binding of lectins to lymphoid cells induces a variety of surface and metabolic changes including the stimulation of DNA synthesis and proliferation of these cells. There is also recent evidence that some lectins will inhibit the growth of neoplastic lymphoid cells in tissue culture. This suggests that the interaction of normal and transformed lymphoid cells with lectins may offer a unique system for the comparison of the surface behavior and biochemistry of cells in the naturally quiescent, mitogen-stimulated, continuously dividing, and induced quiescent states. This project proposes to study the differential effects of lectins and chemically-modified lectins on the growth control of transformed and non-transformed cells and to identify the receptor-cytoplasmic interactions that are associated with the stimulation of cells or the arrest of their growth. Extension of these studies has implications for a variety of other surface-to-nuclear interactions as well as for the practical regulation of neoplastic responses.